An aircraft comprises a large number of devices, of various kinds, mechanical, hydraulic, electrical or electronic whose proper operation is essential in the course of a flight. To improve the degree of confidence accorded to these devices, each of them is subjected to monitoring of their proper operation consisting in monitoring the fundamental parameters and in automatic or semi-automatic tests of operation, followed by fault diagnosis that may lead to the issuing of fault messages. This monitoring of proper operation, associated with a device, is known by the name BITE function, derived from the acronym “Built In Test Equipment”. The set of fault messages is in general grouped together initially by main function of an aircraft within the computer in charge of the function. Such is the case for example for the monitoring of the faults related to automatic piloting AP or to the flight management system FMS. Such is also the case for the alert messages gathered in the FWS (“Flight Warning System”) computer. Subsequently, a so-called centralized-maintenance computer gathers and organizes the fault messages and the alert messages originating from the set of computers of the aircraft. This centralized facility, known by the name “Central Maintenance Computer”, is accessible to the crew through an interface with keyboard and screen in the cockpit of the aircraft; it is also accessible to an operator during maintenance operations carried out when the aircraft is on the ground.
The main function of the centralized maintenance is to carry out, in real time or at the end of the flight, a diagnosis of the general situation of the aircraft on the basis of a summary of the fault and alert messages received from the various devices of the aircraft. It also fulfils other functions such as the correlation of the fault messages received with the alerts received at the level of the flight deck, the conduct of the particular tests on the devices undertaken on request by an operator, or the drafting of reports destined for the ground maintenance teams. These maintenance reports incorporate a log of the fault messages issued by the various devices of the aircraft and alerts presented to the crew as well as the summary of the fault messages carried out as a last resort. More generally, they contain all the information about the operating states of the devices, liable to facilitate the work of the ground maintenance team.
Conventionally, through its functionality, the system for centralized maintenance is connected to several tens of devices or computers, each being able potentially to generate tens or indeed hundreds of fault messages.
The development and maintenance of such a system is complex and expensive since it depends not only on the technical specifications of the devices of the aircraft but also on the operational customs and procedures of aircraft manufacturers and operators. The function adheres strongly to the aeroplane's system definition. Fine tuning is lengthy and complex due to the very large number of connected devices to be processed (more than a hundred computers for a high-capacity aircraft) and to the diversity of the protocols. The design of such a system is prone to numerous iterations of software development, as the aircraft manufacturer converges in maturity in the expression of his requirement, that is to say in the knowledge of the behaviour of the devices in an empirical manner, before and after commissioning into service.
It is therefore important to be able to upgrade the system for centralized maintenance, for example for the modification of the man machine interface (MMI), the addition of parameters, the addition of devices, or the improvement of the diagnoses, without any software certification activity. This condition is not realized by the systems for centralized maintenance of the prior art which exhibit the characteristic of being developed, having regard to the certification constraints, as a monolithic sequential code. Lengthy design and validations, carried out at the end of an aircraft's development cycle, are necessary to integrate into the system for centralized maintenance the upgrades of the other sub-systems of the aircraft and of their diagnostic functions. Regular software updates must be organized during the development and in a subsequent phase of commercial operation of the aircraft.